Where do I find the skirmish maps for organized play as well as the Missions? Are they in the expansions. I only have the base set.
Thanks in advance.
Skirmish Maps for Organized play.
They are listed in the "Imperial Assault Tournament Regulations" document here: https://www.fantasyflightgames.com/en/products/star-wars-imperial-assault/?section=support#/support-section
The legal maps are listed on page 4 at the bottom-left of the page. None of the current legal maps are found in the core set...but they all use the tiles from the core set. The maps (and where to find them) are these:
--Nelvaanian War Zone (Princess Leia pack...need the Return to Hoth tiles to build it)
--Training Ground (Stormtrooper pack...need only the Core Set to build it)
--Mos Eisley Cantina (Twin Shadows box...need tiles from that set to build it)
So right now you need to own (or at least have access to) the tiles from all 3 boxed expansions. But before thinking you need to go out and spend all that money, I'd suggest that you ask around if anyone has some tiles that you can borrow. You can also find the tiles for a decent price on eBay. But if you end up liking Skirmish then you'll likely end up buying all the expansions anyway, so you might as well save the money and buy the full expansions straight out, rather than buying the tiles separately).
Edited by thereisnotryThanks. Very helpful response.
They are listed in the "Imperial Assault Tournament Regulations" document here: https://www.fantasyflightgames.com/en/products/star-wars-imperial-assault/?section=support#/support-section
The legal maps are listed on page 4 at the bottom-left of the page. None of the current legal maps are found in the core set...but they all use the tiles from the core set. The maps (and where to find them) are these:
--Nelvaanian War Zone (Princess Leia pack...need the Return to Hoth tiles to build it)
--Training Ground (Stormtrooper pack...need only the Core Set to build it)
--Mos Eisley Cantina (Twin Shadows box...need tiles from that set to build it)
So right now you need to own (or at least have access to) the tiles from all 3 boxed expansions. But before thinking you need to go out and spend all that money, I'd suggest that you ask around if anyone has some tiles that you can borrow. You can also find the tiles for a decent price on eBay. But if you end up liking Skirmish then you'll likely end up buying all the expansions anyway, so you might as well save the money and buy the full expansions straight out, rather than buying the tiles separately).
I just bought the core and was wondering what I need to buy next. I guess the primary expansions are the priority then, right? Any recommendations on good Imperial expansions to purchase after that?
If you are not playing in tournaments straight away you can print out the maps instead and have a play first.
The best Imperial Expansion is a second Core Set.
The best Imperial Expansion is a second Core Set.
That's not so true anymore. A second set of elite Stormies is great, either from a second core or a stormie blister. Get to one of the spring tournaments if you can and you have your second royal guard card. The real value from the core is then only in the option to field more officers and a second probe droid. The Hoth Box with eltie Snowtrooper is also great for Trooper lists.
Sadly you should get Weiss because of the Card "New Orders" and Han Solo for "Inspiring Speech" and a Rebel trooper set for "Grenadier" and "Reinforcements" if you want to go the trooper style.
And didn't "rule by fear" come out in Kayn somos' pack?
Here's an option if you live in New Jersey: borrow from me! 
Seriously, if you find a local gaming group for IA then I think you'll probably find one or two people who would be happy to let you borrow some stuff as you get started. I know that I'd be more than happy to help out somebody who's just getting into the game.
As for which expansions to get, it seems like you generally get the most value for your money from the boxed expansions (Twin Shadows and Return to Hoth...tiles, figures, cards, etc). My suggestion is to get the boxed expansions that you don't currently have and then get any individual blister packs for their specific contents as you need them.
However, I should mention that I'm one of those guys who wants to be able to play any squad type and who also tends to go all-in when they find a game that they like.